Virtual circuit management in cellular telecommunications

ABSTRACT

A method and apparatus for managing a virtual circuit network is disclosed that enables hand-off management. An illustrative embodiment establishes a virtual ciruit by receiving, at a radio port, a virtual circuit identifier from a wireless terminal and attaching the virtual circuit identifier to an OA&amp;M cell. The radio port then transmits, over a pre-established unidirectional virtual ciruit, the OA&amp;M cell to a radio port manager.

FIELD OF THE INVENTION

The present invention relates to telecommunications systemsarchitecture, in general, and more particularly, to a method andapparatus for managing virtual circuits for cellular telephony.

BACKGROUND OF THE INVENTION

FIG. 1 depicts a schematic diagram of a portion of a typical wirelesscommunications system in the prior art, which system serves a number ofwireless terminals that are situated within a geographic area. The heartof a typical wireless system is known as a Mobile Switching Center("MSC") or, alternatively, as a Mobile Telephone Switching Office("MTSO"). Typically, the MSC is connected to a number of base stations,which are dispersed throughout the geographic area serviced by thesystem, and the local and long-distance telephone networks. The MSC isresponsible for, among other things, routing or "switching"conversations between wireless terminals and between a wireless terminaland a wireline terminal, which is connected to the wireless system viathe local and/or long-distance networks.

The geographic area serviced by the wireless system is partitioned intoa number of spatially distinct areas called "cells." As depicted in FIG.1, each cell is schematically represented by a hexagon; in practice,however, each cell usually has an irregular shape that depends on thetopography of the terrain serviced by the system. Typically, each cellcontains a base station, which comprises the antennas and radios thatthe base station uses to communicate with the wireless terminals andalso comprises the transmission equipment that the base station uses tocommunicate with the MSC.

For example, when wireless terminal 111 desires to communicate withwireless terminal 112, wireless terminal 111 sends its data to basestation 100, which relays the data to MSC 120. Upon receipt of the data,and with the knowledge that it is intended for wireless terminal 112,MSC 120 then returns the data back to base station 100, which relays thedata, via radio, to wireless terminal 112. Although it may appear oddthat the data must be transmitted from the base station to the MSC onlyto be returned, it is necessary when base station 100 does not haveswitching capability. In general, the link between the base station andthe MSC carries a great quantity of data, and now that wireless systemsare carrying substantially more video and high-speed data than they havein the past, it has become very important for the link to and from thebase stations to be capable of efficiently carrying large quantities ofdata.

SUMMARY OF THE INVENTION

A method and apparatus for managing a virtual circuit network isclaimed, which facilitates hand-off management in a cellulartelecommunications sytem. An illustrative embodiment establishes avirtual circuit by receiving, at a radio port, a virtual circuitidentifier from a wireless terminal and attaching the virtual circuitidentifier to an OA&M cell. The radio port then transmits, over apre-established unidirectional virtual circuit, the OA&M cell to a radioport manager.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a schematic diagram of a typical wireless communicationsystem in the prior art.

FIG. 2 depicts a schematic diagram of a telecommunications systemarchitecture in accordance with the exemplary embodiment of the presentinvention.

FIG. 3 depicts a diagram of the message flow paths among the logicalsubsystems that comprise the exemplary embodiment of the presentinvention.

FIG. 4 depicts a schematic diagram of typical message flows involvingsome of the logicial subsystems that comprise the exemplary embodiment.

FIG. 5 depicts a diagram of typical signaling connections in theexemplary embodiment.

FIG. 6 depicts a diagram of the message flows in another illustrativecontroller as shown in FIG. 3.

FIG. 7 depicts a diagram of illustrative message flows for a wirelessterminal originated call.

FIG. 8 depicts a diagram of illustrative message flows for a wirelessterminal terminated call.

FIG. 9 depicts a block diagram of the interconnectivity of the networkelements in the exemplary embodiment.

FIG. 10 depicts a block diagram of a radio port in the exemplaryembodiment.

FIG. 11 depicts a block diagram of the Packet Processing Complex.

FIG. 12 depicts a block diagram of the Narrowband Internetworking Unit.

FIG. 13 depicts a block diagram of the Wireless Control Complex.

FIG. 14 depicts a block diagram of the Wired Network Control Complex.

FIG. 15 depicts a block diagram of the Application Server Complex.

FIG. 16 depicts a block diagram of the Network Management Complex.

FIG. 17 depicts the timing of the typical message flows for a wirelessdirected hand-off using pre-established uni-directional virtual channelconnections.

FIG. 18 depicts the timing of the typical message flows for a wirelessdirected hand-off using pre-established bi-directional virtual channelconnections.

FIG. 19 depicts the timing of the typical message flows for a wirelessdirected hand-off using no pre-established virtual channel connections.

FIG. 20 is a typical configuration for the RF Distribution Unit.

FIG. 21 is another typical configuration for the RF Distribution Unit.

FIG. 22 is another typical configuration for the RF Distribution Unit.

DETAILED DESCRIPTION

1. Introduction

For pedagogical reasons, the detailed description is partitioned intofive sections. This section is an overview of the exemplary embodimentof the present invention, which preferably comprises an ATM basedtelecommunications network architecture that is advantageously capableof supporting both wireless and wireline telecommunications. Section IIdescribes the logical subsystems that compose the exemplary embodiment.The message flows associated with wireless terminal registration, callorigination and call termination in the exemplary embodiment aredescribed in Section III. Section IV describes how the logicalsubsystems of Section II are grouped into functional modules in theexemplary embodiment, and Section V describes hand-off management inaccordance with the exemplary embodiment.

One goal of the exemplary embodiment is to exploit the functionalityprovided by ATM technology to reduce equipment and operating costs. Thepresent invention is suitable for any access technology (e.g., AMPS,TDMA, CDMA) although the preferred embodiment uses CDMA because italready uses packetized data.

A high level depiction of the architecture of the exemplary embodimentis given in FIG. 2. Its salient advantages preferably include:

1. the redistribution of the network systems in a modular fashion amonga plurality of processing elements or servers (e.g., 211, 213, etc.),which are interconnected by a broadband network (e.g., an ATM network,B-ISDN) that uses "cells" to transport information. This approachadvantageously facilitates the addition of processing elements to thesystem, at any time, to accommodate increased demand on the system. Itis also advantageous for restoration and failure control.

2. the dynamic allocation of resources. For example, for a given call,only a subset of the processing elements in the system may be required,depending on whether the call is land terminated, wireless terminalterminated, or whether it is a voice, data or multimedia call. In theexemplary embodiment, advantageous connection set-up procedures enable agiven call to only consume those resources in the system that arenecessary for the completion of the call.

3. extensive exploitation of off-the-shelf components. The broadbandnetwork spanning the service area preferably consists of a combinationof ATM macro- and micro-switches and ATM multiplexors arranged in alocal-area or metropolitan-area network. ATM network components areoff-the-shelf units and are already available from severalmanufacturers. Access to the Public Switched Telephone Network ("PSTN")is provided via ATM Switches and/or stand-alone broadband/narrowbandinterworking units (shown in FIG. 9).

4. lower system cost. Cell sites ("CS") in the exemplary embodiment arepreferably replaced by one or more radio ports ("RP"). Functionally,radio ports are different from cell sites since most of the controlfunctions associated with cell sites are advantageously moved back intothe network where they can be accessed/shared by any radio port in thesystem. This facilitates miniaturization and lowers overall system costby allowing N+1 sparing of the control function. Fault recovery incurrent cellular systems is accomplished via 1+1 sparing of thecontrollers.

5. low cost off-the-shelf ATM multiplexors, which can be used toconcentrate traffic from multiple radio ports to benefit from theeconomy of scale in wide bandwidth pipes. This is one reason why in theexemplary embodiment the ATM transport is preferably extended all theway to the radio ports.

6. the separation of connection management and call management, whichenables the accelerated development and introduction of advancedservices such as video, imaging, and multimedia. This separation alsoadvantageously facilitates the real-time allocation of network resources(e.g., frame selectors, speech codecs and wireless network controllers).

7. the "user process," which serves as a proxy for the user terminal andwhich facilitates the set-up of calls involving advanced services (e.g.,video). This facilitates call registration without overconsuming costlywireless bandwidth.

8. simplified call-routing and faster call set-up through the use ofwireless "fixed points."

9. enhanced services to roaming subscribers through the use of a "HomeCall Manager." In contrast to the Home Location Register/VisitorLocation Register ("HLR/VLR") approach of systems in the prior art oftransferring subscriber profiles between home and serving systems, callcontrol is preferably the responsibility of a subscriber's home serviceprovider regardless of the subscriber's location. Connection management,in constrast, is preferably performed by the serving system. This isfacilitated by the availability of high bandwidth pipes to the homesystem.

10. the simplification of information and resource management throughthe use of "gateways," which separate the wireless vs. fixed and localvs. global aspects of providing service.

11. the support of expedited mobile-assisted and mobile-directedhand-off through the pre-establishment and dissemination of virtual pathconnection/virtual circuit connection ("VPC/VCC") routing tables.

12. in-band performance monitoring and supervisory capabilities, whichare used for hand-off management, fault management, configurationmanagement, connection quality control and radio link quality control.

The book ISDN and Broadband ISDN, 2nd Ed. by William Stallings,Macmillan Publishing Company (1992), provides a good background on ATMtechnology and ATM adaptation layer protocols and is hereby incorporatedby reference as if set forth in its entirety. The disclosure of threeU.S. patent applications, all assigned to the assignee of thisapplication are incorporated by reference: (1) Ser. No. 08/323,958,entitled "Broadband Adaptation Processing," filed Oct. 17, 1994, (2)Ser. No. 08/164,514, U.S. Pat. No. 5,473,674, entitled "A SignalingSystem for Broadband Communications Networks," filed Dec. 9, 1993, and(3) Ser. No. 08/164,521, U.S. Pat. No. 5,563,939, entitled "DirectSignaling System for Narrowband Communications Networks," filed Dec. 9,1993. Further, the disclosure of D. J. Goodman, U.S. Pat. No. 4,916,691,issued Apr. 10, 1990 is also incorporated by reference.

2. Network Subsystems

The exemplary embodiment preferably comprises conceptual "subsystems"that establish, supervise and release both wireless and wireline calls.Objects that are tightly coupled are grouped into "subsystems." Itshould be understood that the partitioning of the exemplary embodimentinto these conceptual subsystems is only a functional partitioning andin no way should restricts the manner in which embodiments of thepresent invention can be implemented.

For example, each subsystem can be implemented on its own platform; orseveral subsystems can share a hardware platform, or one or moresubsystems can be distributed across multiple platforms. Except whenexplicitly stated otherwise, a reference to a particular ManagementSubsystem or Handler in this specification refers to a logical subsystemrather than the hardware implementation of that subsystem.

2.1 List of Network Subsystems

The exemplary embodiment preferably comprises 25 subsystems, which, forpedagogical reasons, are advantageously divided into six groupsaccording to their primary role. The six groups are:

1. Packet Transport--The subsystems in this group preferably share theresponsibility for transporting user information and system data betweennetwork elements. The subsystems in this group are:

Radio Port Subsystem ("RP");

Radio Port Multiplexing Subsystem ("RPM");

Packet Handling Subsystem ("PH");

Signaling Message Handling Subsystem ("SMH"); and

Control Channel Message Handling Subsystem ("CCMH").

2. Channel Management--The subsystems in this group are responsible forallocating communications resources (e.g., channels). The subsystems inthis group are:

ATM Channel Management Subsystem ("AChM"); and

Radio Port Channel Management Subsystem ("RPChM").

3. Call Control--The subsystems in this group are responsible forprocessing service requests, and include the following:

Call Management Subsystem ("CM"); and

User Signaling Server Subsystem ("USS").

4. Connection Control and Mobility Management--The subsystems in thisgroup are concerned primarily with connection control and management formobility. The group includes the following:

Configuration and Location Management Subsystem ("CoLoM");

ATM Connection Management Subsystem ("ACoM");

Radio Channel Quality Management Subsystem ("RCQM"); and

Wireless-Wired Gateway Connection Management Subsystem ("WWGCoM").

5. Network Management--The subsystems in this group are responsible fortraditional OA&M processing as well as those aspects of OA&M unique towireless and ATM applications. The group consists of the following:

Billing Subsystem;

Security Subsystem;

ATM Network Management Subsystem ("ANM"); and

Wireless-Wired Gateway Network Management Subsystem ("WWGNM").

6. Applications and Services--The subsystems in this group are used tosupport requests for services that require significant amounts ofapplication-specific processing. They include:

Speech Handling Subsystem ("SH");

Multimedia Multiparty Management Subsystem ("MMM");

Packet Data Handling Subsystem ("PDH");

Circuit-Switched Data Handling Subsystem ("CDH");

SS7 Message Handling Subsystem;

Fax Handling Subsystem;

Message Services Subsystem; and

Video Services Subsystem.

2.2 System Operation

This section is intended to illustrate by simple example how thesubsystems identified above preferably work together to support typicalcalls in accordance with the exemplary embodiment.

Referring to FIG. 3, when a packet transmitted by a wireless terminal("WT") is received by a radio port, it is demodulated, decoded,encapsulated in an ATM cell and forwarded to the Radio Port MultiplexingSubsystem. The Radio Port Multiplexing Subsystem collects ATM cells fromseveral radio ports and multiplexes them onto a higher bandwidthfacility for more cost-effective transport to the ATM network.

The ATM network delivers the ATM cells to the Packet Handling Subsystemwhere, for the first time, the information content of the packet fromthe wireless terminal is examined. If the packet contains compressedspeech data, it is preferably repackaged in an ATM cell and delivered tothe Speech Handling Subsystem where the data is decoded and, in general,sent into the PSTN. If the remote end is capable of accepting codedspeech, the Speech Handling Subsystem can be bypassed. Similarly, echocancellation may or may not be included in the path depending on thepresence or absence of a 4-wire to 2-wire conversion in the path to theremote terminal.

If the packet delivered to the Packet Handling Subsystem containscircuit mode user data, the contents are encapsulated in an appropriateATM Adaptation Layer ("AAL") and sent to the Circuit-Switched DataHandling Subsystem that implements the link layer functions and errorrecovery strategies for the air-interface. Depending on the requirementsof the application, the Circuit-Switched Data Handling Subsystem mayalso terminate the transport layer for the radio interface and begin anew one for the land network, thus performing an internetworkingfunction as well. Packets delivered to the Packet Handling Subsystemcontaining data for other user services, e.g., packet data or multimediaservices, as well as internetworking with B-ISDN are routed to therelevant application data handling subsystem in the same way.

In-band signaling messages, which are typically transmitted in segmentsover the air-interface, are assembled by the Packet Handling Subsystembefore being forwarded to the Signaling Message Handling Subsystem. TheSignaling Message Handling Subsystem preferably parses the messages andforwards them to the appropriate control subsystem.

Messages containing radio channel quality measurements are carriedin-band on the radio channel and are routed by the radio port, thePacket Handling Subsystem and the Signaling Message Handling Subsystemto the Radio Channel Quality Management Subsystem. When the quality ofthe radio channel falls below a pre-established level, the Radio ChannelQuality Management Subsystem notifies the Radio Port Channel ManagementSubsystem of the need for a hand-off. Alternatively, in amobile-directed hand-off, the hand-off request is initiated by thewireless terminal on an access channel and routed by the target radioport to the Control Channel Message Handling Subsystem and directly tothe Radio Port Channel Management Subsystem. The Radio Port ChannelManagement Subsystem is responsible for all aspects of radio resourcemanagement, including coordination of the activities needed to effect asuccessful hand-off.

Call control messages, in constrast, are sent to the User SignalingServer Subsystem. The User Signaling Server Subsystem converts theservice-related request into a form compatible with the core callprocessing platform and forwards it to the Call Management Subsystem.The Call Management Subsystem checks to see whether or not thesubscriber is eligible to receive the requested service and enlists theaid of application-specific subsystems as needed to determine the typeof connection that is required. Once the connection requirements areadvantageously established, the Call Management Subsystem contacts theATM Connection Management Subsystem and instructs it to establish theappropriate connection. The ATM Connection Management Subsystemdetermines the optimal route for the connection and, in turn, contactsthe ATM Channel Management Subsystem. The ATM Channel ManagementSubsystems may be distributed across all the network nodes involved inthe connection. The ATM Channel Management Subsystem terminates thechain of events by allocating packet transport resources and updatingthe appropriate virtual path indicator/virtual circuit indicator("VPI/VCI") translation tables.

Preferably, there is another important function performed by the PacketHandling and Signaling Message Handling Subsystems, namely that ofacting as "wireless fixed points." That is, the Packet HandlingSubsystem and the Signaling Message Handling Subsystem help makehand-offs transparent to the rest of the network. If the User SignalingServer Subsystem needs to contact a wireless terminal, for example, itsimply sends the data it wants delivered to the wireless terminal to theSignaling Message Handling Subsystem. The Signaling Message HandlingSubsystem constructs the appropriate message and forwards it to thePacket Handling Subsystem, where it is merged with the user data streamand sent to the radio port (or multiple Radio ports during softhand-offs) with which the wireless terminal is communicating. If theSignaling Message Handling Subsystem and Packet Handling Subsystem didnot perform the wireless fixed-point function, each control subsystemwould have to track the whereabouts of every wireless terminal it servesdown to the serving radio port level.

Messages received by a radio port on the reverse control channel (accesschannel) are routed directly to the Control Channel Message HandlingSubsystem over PVCs. The Control Channel Message Handling Subsystem andSignaling Message Handling Subsystem are similar in many respects. Both,for example, implement a discrimination function for parsing outmessages to the control subsystems. Both also play key roles in relayinginformation from the system to the wireless terminal. One SignalingMessage Handling Subsystem resource is preferably dedicated per activewireless terminal during a call; one Control Channel Message HandlingSubsystem resource is preferably dedicated permanently per radio port.

The Control Channel Message Handling Subsystem routes power-upregistration information to the Configuration and Location ManagementSubsystem. The Configuration and Location Management Subsystem, beingresponsible for subsystem resource assignment, uses this information toinstantiate a User Process ("UP") in the aforementioned User SignalingServer Subsystem and to allocate Wireless-Wired Gateway ConnectionManagement Subsystem resources. The Wireless-Wired Gateway ConnectionManagement Subsystem oversees the per-call establishment of connectionsbetween the wireless fixed point (i.e., the Packet Handling Subsystemand Signaling Message Handling Subsystem) and the radio port.

The Control Channel Message Handling Subsystem forwards subsequentregistration attempts directly to the appropriate User Process,consulting the Configuration and Location Management Subsystem only whenit receives a message from a wireless terminal it knows nothing about.This is advantageously done to keep the Configuration and LocationManagement Subsystem from becoming a bottleneck due to numerous locationupdates.

The Control Channel Message Handling Subsystem also routes requests forservice directly to the User Process. The User Signaling ServerSubsystem housing the User Process processes such requests inessentially the same manner as those routed to it via the SignalingMessage Handling Subsystem.

Two of the subsystems not shown in FIG. 3 are the ATM Network ManagementSubsystem and the Wireless-Wired Gateway Network Management Subsystem.The ATM Network Management Subsystem is responsible for the maintenanceand configuration functions normally associated with ATM networks,including populating the ATM Connection Management Subsystem routingtables. The Wireless-Wired Gateway Network Management Subsystem, inconstrast, is responsible for establishing the signaling links betweensubsystems unique to the wireless application (e.g., radio port, PacketHandling Subsystem and Control Channel Message Handling Subsystem). TheWireless-Wired Gateway Network Management Subsystem is also responsiblefor pre-establishing the matched virtual circuit identifier ("VCID")sets used for facilitating rapid hand-offs. This process is describedmore fully in Section V below.

The roles played by the other subsystems identified in Section 2.1 butnot depicted in FIG. 3 are described in Section 2.1.3 along with a moredetailed description of the subsystems previously discussed.

2.3 Subsystem Descriptions

2.3.1 The Packet Transport Group of Subsystems

2.3.1.1 Radio Port Subsystem

The Radio Port Subsystem preferably provides the physical transportrelated functions associated with the air-interface, including frequencytranslation and modulation/demodulation. Moreover, since soft-decisiondecoding is more conveniently implemented where the physical layer ofthe radio interface is terminated, channel coding/decoding andinterleaving/deinterleaving are also advantageously regarded as RadioPort Subsystem functions. Furthermore, depending on the air-interface,multiple channel decoders may advantageously be implemented to supportvariable rate coding strategies and/or to distinguish packets containinguser data from those carrying blank and burst signaling.

In addition to terminating the air-interface physical layer, the RadioPort Subsystem also terminates the B-ISDN physical layer, the ATM andAAL layers for at least four pre-established VPCs and their associatedVCCs. One VP/VC is used to transport decoded traffic channel packetsbetween the radio port and Packet Handling Subsystem. The VCCsassociated with this VPC are allocated on a per-call basis by the RadioPort Channel Management Subsystem in response to a request for aconnection from the Wireless-Wired Gateway Connection ManagementSubsystem. Depending on the hand-off mechanism in effect, more than oneVP/VC may be assigned to a given call by the Radio Port ChannelManagement Subsystem. A second VPC is used to support the pilot, pagingand access channel processes running in the Control Channel MessageHandling Subsystem. The third VPC is used to access the radio resourceallocation and ATM channel management functions provided by the RadioPort Channel Management Subsystem. The fourth is used by the RadioChannel Quality Management Subsystem to download dynamic power controlinstructions.

For cellular coverage the Radio Port Subsystem is preferably distributedacross multiple hardware "boxes," or "radio ports." Each radio portprovides radio coverage for a specific geographic area. The number andplacement of Radio ports is dependent on several factors, includingtopography, multiple access technology, capacity, frequency band, zoningrules and the availability and cost of network access. Furthermore, someradio ports can only support a few users (e.g., picocells), while otherradio ports can support hundreds of users (e.g., macrocells). Regardlessof their size or number or the access technology they support, theprimary function of the individual radio port remains the same as in theprior art: to convert electromagnetic signals to bits, and vice-versa.

2.3.1.2 Radio Port Multiplexing Subsystem

The preferred function of the Radio Port Multiplexing Subsystem is toconcentrate the traffic from multiple radio ports to achieve the economyof scale normally attained from transport via higher bandwidthfacilities. Note that the Radio Port Multiplexing Subsystem preferablydoes not perform any control functions. In fact, the Radio PortMultiplexing Subsystem does not even terminate AALs. As such, the RadioPort Multiplexing Subsystem is not the same as, nor should it becompared to or confused with, the radio port controller elements ofother architectures (e.g., GSM and PACS). All control functions normallyassociated with radio port controllers are advantageously moved backinto the network where they can be accessed by all the radio ports inthe system, not just by the radio ports connected to a controller viadedicated, nailed-up links. The separation of the control andmultiplexing functions also enables the use of industry-standard ATMmultiplexors as a platform for the Radio Port Multiplexing Subsystem.

2.3.1.3 Packet Handling Subsystem

The Packet Handling subsystem terminates network-radio port VCCs andtheir associated AALs. Depending upon the requirements of theair-interface, it may also terminate the traffic channel link layerand/or implement a frame-selection function to support soft hand-offs.Regardless of the air-interface, however, the Packet Handling Subsystemis always responsible for separating speech, user-data and in-bandsignaling into separate streams, and for directing each stream to theappropriate subsystem for further processing (or concatenating separatestreams for transmision to the wireless terminal).

In the reverse direction, the Packet Handling Subsystem directs speechpackets from the Radio Port Subsystem to the Speech Handling Subsystemand user-data packets to the appropriate data handling subsystem.In-band signaling messages are forwarded to the Signaling MessageHandling Subsystem once they are advantageously assembled. In theforward direction, the Packet Handling Subsystem combines signaling datafrom the Signaling Message Handling Subsystem with speech data from theSpeech Handling Subsystem, in accordance with the rules of theassociated air-interface. It then encapsulates the results in an AAL andsends the ATM cells to the radio port serving the wireless terminal overthe appropriate VP/VC (multiple VPs/VCs in the case of soft hand-off).

As noted previously in Section 2.2, the Packet Handling Subsystem alsoserves as the fixed-point for the call. That is, while it may benecessary to change the VPs/VCs between the Packet Handling Subsystemand Radio Port Subsystem during a call to maintain the radio link, theVPCs/VCCs between the Packet Handling Subsystem and the other subsystemsit communicates with only change during a call in response to componentfailures or requests for hard-hand-offs to other systems.

2.3.1.4 Signaling Message Handler Subsystem

The Signaling Message Handling Subsystem performs two basic functions:

parsing out reverse traffic channel signaling messages to theappropriate control subsystem; and

acting as the signaling fixed-point for the transmission of messages towireless terminals on forward traffic channels.

The Signaling Message Handling Subsystem preferably communicates withthe Wireless-Wired Gateway Connection Management Subsystem, the UserSignaling Server Subsystem, the Radio Channel Quality ManagementSubsystem and the Packet Handling Subsystem. As depicted in FIG. 4, thisis preferably done over pre-provisioned VP/VCs when the subsystems arenot co-located.

The parsing and fixed-point functions of the Signaling Message HandlingSubsystem are also illustrated in FIG. 4. For example, the SignalingMessage Handling Subsystem forwards:

"Connect Order Messages" indicating acceptance of incoming calls to theWireless-Wired Gateway Connection Management Subsystem,

"Power Measurement Report Messages" containing wireless terminalassisted hand-off data to the Radio Channel Quality ManagementSubsystem, and

"Release Order Messages" ending calls to the User Signaling ServerSubsystem.

Messages passed on by the Signaling Message Handling Subsystem to thePacket Handling Subsystem as part of the Signaling Message HandlingSubsystem's fixed-point role include:

"Alert With Information Messages" from the Wireless-Wired GatewayConnection Management Subsystem indicating the presence of incomingcalls, and

"Flash with Information Messages" from the User Signaling ServerSubsystem system supporting the call-waiting feature.

Note that the above lists are by no means exhaustive and may varyconsiderably from one air-interface to another. However, for a given"suite" of air-interfaces, e.g., AMPS, the set of forward and reversetraffic channel messages and their content tend to be similar. As such,the Signaling Message Handling Subsystems for the members of the suiteare be remarkably similar, even though corresponding messages may beformatted (and named) quite differently.

2.3.1.5 Control Channel Message Handler Subsystem

The Control Channel Message Handling Subsystem performs three functions:

Paging Channel Processing ("PCP");

Access Channel Processing ("ACP"); and

Pilot and Sync Channel Processing ("PSP").

The Control Channel Message Handling Subsystem and Radio Port Subsystemcommunicate directly over pre-established VPs/VCs. The Packet HandlingSubsystem is preferably not in the path because two of its mainfunctions, e.g., frame selection and user data vs. signalingdiscrimination, are not needed to process control channel messagestreams.

In addition to Page messages, the Paging Channel Processing functionalso handles System Parameter, Access Parameter, Neighbor List, and CDMAChannel List messages. These messages are transmitted periodically bythe radio port on the paging channel. For information on CDMA technologyand the internal formatting of CDMA packets, the reader is referred toInterim Standard 95 (alternatively known as PN-3118 and "IS-95"), whichpublished by the Telecommunications Industry Association, WashingtonD.C., and is hereby incorporated by reference as if set forth in itsentirety.

Of particular interest here, because of its impact on the registrationscenarios, is the System Parameter message. Among other things, theSystem Parameter message is used to inform the wireless terminals underwhat circumstances they need to register. There are flags to indicate,for example, whether or not the wireless terminals need to register uponpower-up and/or power-down, when they cross from one "zone" in thesystem to another, or periodically when a registration timer expires. Inother words, with all of these registration options preferablyavailable, there is no need to support procedures in the network foroffering calls to unregistered wireless terminals. As such, noprovisions are advantageously made, for example, to support scenarios inwhich an Origination message is the first indication that the wirelessterminal in question is active in the system.

The primary duty of Access Channel Processing is to route messagesarriving via reverse control channels to the appropriate subsystem forfurther processing. Upon receipt of a Registration message, for example,Access Channel Processing checks to see if it knows how to deliver it tothe User Process representing the wireless terminal. If it doesn't, itpasses the message on to the Configuration and Location ManagementSubsystem which, in turn, instantiate a User Process in the UserSignaling Server Subsystem and tells the Control Channel MessageHandling Subsystem how to communicate with it. Establishing the ControlChannel Message Handling Subsystem to User Process communications linkduring the registration process allows the Control Channel MessageHandling Subsystem to forward subsequent registration messages, as wellas requests for service (i.e., Origination messages) directly to theUser Process. This speeds-up the call establishment process and reducesthe load on the Configuration and Location Management Subsystem.Communications between the Control Channel Message Handling Subsystemand the Configuration and Location Management Subsystem and UserSignaling Server Subsystems are carried over pre-established VPs/VCs.

It should be noted that alternative schemes wherein all Registration andOrigination messages are forwarded to the Configuration and LocationManagement Subsystem for subsequent delivery to the User Process canalso be implemented. The advantage of embodiments incorporating thisscheme is that it eliminates the need for the Control Channel MessageHandling Subsystem to maintain Control Channel Message HandlingSubsystem-User Signaling Server Subsystem routing tables.

If the system supports short message services, the Control ChannelMessage Handling Subsystem also maintains communications links to theMessage Services subsystem.

2.3.2 The Channel Management Group of Subsystems

2.3.2.1 ATM Channel Management Subsystem

The ATM Channel Management Subsystem preferably manages "channel" andVP/VC translation tables. A channel means a point-to-pointunidirectional link within an ATM interface between a user/server and aswitch, between two switches, between a switch and a cross-connect, orbetween cross-connects. It corresponds to the virtual channel link("VCL") or virtual path link ("VPL") as defined in CCITT RecommendationI.113. The VP/VC Translation Table lists the interconnections ofchannels that support connections passing through switches orcross-connects. The functions of the channel manager preferably are:

reserve, allocate, modify, drop, and maintain channels on all the portsof the switch or end-point (user or server) with which this channelmanager is associated;

maintain VP/VC Translation Table entries for connections that traversethe switch with which the channel manager is associated; and

provide hand-off control by reassigning channels and VP/VC translationtable entries as needed while a wireless terminal moves.

The ATM Channel Management Subsystem is preferably distributed acrossall the network elements, one instance of the subsystem is implementedper network element. Functionally, these channel managers are used tohandle channels that are needed both for switched connections on a percall basis, as well as channels used in provisioned connections, which,for example, are needed to support fast hand-off procedures. It shouldbe noted that ATM Channel Management Subsystems manage channelidentification allocation (VP/VC allocation) and resource verificationover single links only. They do not have a global view of the networkand are preferably not involved in selecting routes.

2.2.2 Radio Port Channel Management Subsystem

The Radio Port Channel Management Subsystem is responsible for:

RF channel management; and

Radio Port Subsystem ATM channel management.

In its role as RF channel manager, the Radio Port Channel ManagementSubsystem preferably selects the channel, subchannel, timing offset,etc., that is used to handle each call. The data needed by the RadioPort Subsystem to establish and maintain radio links is delivereddirectly via pre-established VP/VC. Wireless terminal stationparameters, in contrast, are sent to the Control Channel MessageHandling Subsystem. There, the Paging Channel Processing functionconstructs a Channel Assignment message and sends it to the servingradio port for subsequent transmission to the wireless terminal.

The Radio Port Channel Management Subsystem RF channel managementfunction is also responsible for supervising hand-offs. This involves:

identifying target radio ports based on data supplied by the RadioChannel Quality Management Subsystem,

executing the appropriate call processing algorithm, and

working with the ATM Channel Management Subsystem to modify VP/VCtranslation table entries to reflect the fact that the connection hasbeen altered.

The latter function is actually part of the other role played by theRadio Port Channel Management Subsystem, i.e., that of ATM channelmanager for the radio ports. In this capacity the Radio Port ChannelManagement Subsystem is also responsible for populating and updating thetables mapping VP/VCs to radio port channels and subchannels, as well asperforming the functions identified in the previous section.

2.3.3 The Call Control Group of Subsystems

2.3.3.1 Call Management Subsystem

The Call Management Subsystem processes "calls," which are defined asassociations between user applications and servers. Its specificfunctions include:

providing the capability to establish, modify and release calls,

maintaining subscriber profiles,

facilitating user-to-user and user-to-network negotiation of options andcheck for user/server status and compatibility,

providing service invocation and coordination functions,

recognizing any need for special resources, such as protocol converters,

maintaining call state and configuration information, and

managing call reference values and user account information for selectservices.

The Multimedia Multiparty Management Subsystem, Configuration andLocation Management Subsystem and ATM Connection Management Subsystementities are among the other subsystems in the architecture of theexemplary embodiment supported by the Call Management Subsystem.

2.3.3.2 User Signaling Server Subsystem

The User Signaling Server Subsystem manages the life-cycle of UserProcesses ("UPs"). Each User Process acts as an agent for the callcontrol needs of a single wireless terminal. That is, network callprocessing entities communicate with the User Process representing thewireless terminal indirectly, rather than the wireless terminal itself.User Processes are instantiate by the Configuration and LocationManagement Subsystem when the wireless terminal powers-up or otherwisefirst registers in the system. In addition to handling Registrationmessages, User Processes preferably:

tracks the availability and willingness of the wireless terminal toaccept incoming calls,

processes Origination messages, representing wireless terminals innegotiations with the network for requests for service, and

responds to requests from the Wireless-Wired Gateway ConnectionManagement Subsystem to find the radio port serving a particularwireless terminal.

For example, by tracking the busy/idle status of the wireless terminaland knowing which way "MOB₋₋ TERM," a parameter in Registrationmessages, has been set, the User Process is able to limit paging tothose wireless terminals that are available and willing to acceptincoming calls.

In connection with the second item, note that in the event the wirelessterminal has extended capabilities, e.g., it is a multimedia laptop, itmay be necessary for the User Process to communicate with the wirelessterminal to obtain the information it needs to adequately represent thewireless terminal in negotiations with the network. By using the UserProcess as an agent for the wireless terminal, this transfer, of oftensubstantial quantities of data, takes place during the registrationprocess instead of during the call establishment process. This expeditescall set-up. Furthermore, the interworking function provided by the UserProcess encourages the use of simpler terminal equipment and makes itpossible for the network to support a wider variety of terminal designs.

In its role as the subsystem responsible for finding the radio port ableto communicate with the wireless terminal, the User Signaling ServerSubsystem constructs a Page message and sends it to the Control ChannelMessage Handling Subsystem(s) serving the area (i.e., zones) where thewireless terminal last registered. The Paging Channel Processing withineach Control Channel Message Handling Subsystem contacted in turnensures that the Page message is delivered to each radio port from whichthe page is to be broadcasted. The identity of the radio port andControl Channel Message Handling Subsystem that receives the PageResponse message from the wireless terminal is stored in the UserProcess and also sent to the subsystem issuing the "FIND" request.Subsequent communication with the wireless terminal need not involve theUser Process. That is, communication between the wireless terminal andthe network can be carried out directly via the radio port, PagingChannel Processing and Access Channel Processing serving the wirelessterminal once their identity has been determined.

2.3.4 The Connection Control and Mobility Management Group of Subsystems

2.3.4.1 Configuration and Location Management Subsystem

The Configuration and Location Management Subsystem preferably performsseveral functions.

First, it receives registration messages (simpler versions of the airinterface Registration message) from the Access Channel Processing inthe Control Channel Message Handling Subsystem serving the wirelessterminal. If it is a power-up registration, the Configuration andLocation Management Subsystem sends a message to the User SignalingServer Subsystem instructing it to initiate a User Process for thewireless terminal. In addition to the identity of the wireless terminal,the message also contains the list of Control Channel Message HandlingSubsystems serving the radio ports with which the wireless terminal ismost likely to be able to communicate.

To avoid the need to have all messages received by the Control ChannelMessage Handling Subsystem passed on to the Configuration and LocationManagement Subsystem for routing, the Configuration and LocationManagement Subsystem sends each of the Access Channel Processesassociated with one of the Control Channel Message Handling Subsystemson the list instructions as to how to contact the User Process directly.

If it is a power-down registration, the Configuration and LocationManagement Subsystem sends a message to the User Signaling ServerSubsystem instructing it to delete the User Process. If the message fromthe Access Channel Process indicates the registration is zone-based, theConfiguration and Location Management Subsystem first determines whetheror not it is necessary to migrate the User Process to a different UserSignaling Server Subsystem. This may be necessary, for example, if thereare no direct signaling links (VP/VCs) between the Control ChannelMessage Handling Subsystem housing the Paging Channel Processing andAccess Channel Processing in communication with the wireless terminaland the "old" User Signaling Server Subsystem. If it is necessary tomigrate the User Process, the Configuration and Location ManagementSubsystem oversees both the creation of the new User Process and thedestruction of the old one.

If the User Process does not have to be moved, the Configuration andLocation Management Subsystem sends the User Process an updated list ofControl Channel Message Handling Subsystem addresses corresponding tothe new area where the wireless terminal needs to be paged. In this casethe Configuration and Location Management Subsystem must also inform theAccess Channel Processes associated with the new Control Channel MessageHandling Subsystems on the list how to contact the User Process. Thislatter step reduces the load on the Configuration and LocationManagement Subsystem by allowing subsequent Registration messages to berouted directly to the User Process. By allowing Origination messages tobe routed directly to the User Process as well, the last step alsoserves to reduce post-dial delay.

Second, the Configuration and Location Management Subsystem assigns CallManagement Subsystem, ATM Connection Management Subsystem andWireless-Wired Gateway Connection Management Subsystem resources tohandle a given wireless terminal. Some resources, e.g., Call ManagementSubsystem resources, are assigned when a wireless terminal first entersservice. Other resources are assigned during the registration process.ATM Connection Management Subsystem and Wireless-Wired GatewayConnection Management Subsystem (as well as Control Channel MessageHandling Subsystem and User Signaling Server Subsystem) resources fitinto this group. In any case, depending on where the call arrives (i.e.,which network service provider Point-of-Presence ("POP")) and where itneeds to be routed to (e.g., which radio port), some of resources mayneed to be re-allocated in real-time during call establishment. This isalso done under the control of the Configuration and Location ManagementSubsystem.

Third, the Configuration and Location Management Subsystem fieldsrequests from other subsystems as to how to address resources assignedto a given wireless terminal.

Fourth, the Configuration and Location Management Subsystem generatesSetup Segment messages to the ATM Connection Management Subsystem toprovision VP/VCs between different network entities.

Fifth, the Configuration and Location Management Subsystem generatesSetup Connections messages to establish VP/VCs for transportingsignaling messages between network entities. Signaling AALs("S-AALs")are typically used on these connections. As is normally thecase, signaling-AALs are terminated at the connection end-points. If theconnection is a VPC, then the VCI field in the ATM cells is ignored. Anadditional Connection-Less Protocol ("CLP") may be used above thesignaling-AAL to allow for datagram routing of signaling messagesbetween network entities that do not have a direct signaling VP/VC.

2.3.4.2 ATM Connection Management Subsystem

The ATM Connection Manager Subsystem manages Connections,Call-Connection Mappings, Routes, and Segments. A Connection is definedto be a communication path that interconnects multiple users/serversthrough switches. It extends between entities where the ATM AdaptationLayer ("AAL") is terminated. That is, connections terminate on serversand/or user equipment, and not on the switches and multiplexors. TheCall-Connection Mapping function manages the many-to-many relationshipbetween the calls and connections. It indicates the identities of allthe connections that are managed within the context of a given call.

A Route is a path that passes through one or more users/servers andthrough one or more switches. It captures the connection-to-connectionrelationship where multiple connections may be routed on the same ordivergent paths.

A Segment is a concatenation of one or more channels. It may be part ofa connection. In CCITT Recommendation I.610, a "VPC Segment" is definedas a concatenation of VP links that belong to a common administrativedomain, and a "VCC Segment" is defined as a concatemantion of VC linksthat belong to a common administrative domain. Our definition of theword Segment is more general, in that it is simply a concatenation of aset of VP or VC links. Thus, both VCS ("Virtual Channel Segment") andVPS ("Virtual Path Segment") are possible. In most cases, such segmentswill belong to the same administrative domain, but this is not mandatedin our definition. The important difference between operations onconnections and segments is that the former involves interacting withthe AAL at the termination points of the connection, while the latterdoes not involve any AAL termination points.

Thus, the collective functions of the connection manager preferablycomprise:

providing the capabilities to add/drop/modify a connection, wheremodifying a connection includes adding a participant, dropping aparticipant, or changing the quality of service of an existingconnection;

providing common/diverse routing of connections and end-to-end qualityof service computation for connections;

handling multiple connections in a call;

setting up and tearing down segments of a connection; and

determining the need for multiple connections in order to support theconnection requested based on analysis of user addresses (digitanalysis) or the analysis of other parameters (e.g. bi-directionalmulticast that requires mixing of signals).

As an example of the last function, the ATM Connection ManagementSubsystem is responsible for analyzing the calling and called partynumbers (or initiating other dialog with the Call Managers) to determinewhether or not the Speech Handling Subsystem needs to be involved in thecall to convert compressed air-interface speech data to a formcompatible with the network and vice-versa. If the Speech HandlingSubsystem needs to be involved and, as is advantageously the case, theSpeech Handling Subsystem is not co-located with the Packet HandlingSubsystem, multiple AAL terminations are needed. This in turn, impliesthat multiple connections (VP/VCs) need to be established to fulfill thesingle connection setup request sent to the ATM Connection ManagementSubsystem by the Call Management Subsystem. The use of provisioned VPSegments between the Packet Handling Subsystem and Speech HandlingSubsystems simplifies the ATM Connection Management Subsystem's taskconsiderably by reducing the task to one of only communicating with theChannel Managers for the two VP Segments end-points to select a VCwithin this VP Segment to handle the call.

The above example is illustrated in FIG. 5, where CPE A, capable ofhandling 64 kb/s PCM voice, requests a connection to wireless terminalB, which has an interface for 9.6 kb/s voice. This user request isrealized with three connections. The first one extends between CPE A andthe processor supporting the Speech Handling Subsystem function(identified by AAL a terminations). The second connection extendsbetween the Speech Handling Subsystem and the Packet Handling Subsystem(identified by AAL b terminations). Note that the VP Segment is extendedbetween the AAL termination points for this connection. This limits thenumber of points with which the connection manager needs to interactwith to the two VP Segment end-points, i.e., the Packet HandlingSubsystem and Speech Handling Subsystem.

The two signaling connections are shown with dashed lines in FIG. 5. Afew virtual path segments are provisioned in advance, for this purpose.At the time of a call connection request, only a VCI identifying avirtual channel link is selected on any one of these virtual pathsegments. The third connection extends between the Packet HandlingSubsystem and the radio port (identified by AAL c terminations). Again,one VC per wireless terminal connection (in each direction) is allocatedper connection on the provisioned VPSs between these two points. Theradio port maps packets from this to the specific forward trafficchannel assigned to the wireless terminal and vice versa.

A special connection manager, the Wireless-Wired Gateway ConnectionManagement Subsystem, is assigned to handle connections from the PacketHandling Subsystem out to the wireless terminal.

2.3.4.3 Radio Channel Quality Management Subsystem

The Radio Channel Quality Management Subsystem preferably processeswireless terminal assisted hand-off data forwarded to it by theSignaling Message Handling Subsystem. When the data suggests the needfor a hand-off, the Radio Channel Quality Management Subsystem commencesthe hand-off process by contacting the Radio Port Channel ManagementSubsystem via a pre-established VP/VC. The Radio Channel QualityManagement Subsystem also implements forward and reverse power controlalgorithms, downloading updated power levels to the radio port overpre-established, dedicated VP/VCs.

2.3.4.4 Wireless-Wired Gateway Connection Management Subsystem

The Wireless-Wired Gateway Connection Management Subsystem is preferablyresponsible for setting-up and tearing-down connections from the PacketHandling Subsystem out to the wireless terminal. More specifically(referring again to FIG. 5), the Wireless-Wired Gateway ConnectionManagement Subsystem manages connections between radio ports and RadioPort Multiplexing and between Radio Port Multiplexing and PacketHandling Subsystem.

One instance of the Wireless-Wired Gateway Connection ManagementSubsystem is associated with each instance of the Packet HandlingSubsystem. The Wireless-Wired Gateway Connection Management Subsysteminterfaces with the Radio Port Channel Management Subsystem and ATMChannel Management Subsystems to reserve and commit channels and tosetup VP/VC translation table entries in the units they support. It alsocommunicates with the User Signaling Server Subsystem to identify theradio port able to communicate with the wireless terminal. Once theWireless-Wired Gateway Connection Management Subsystem knows theidentity of the radio port able to serve the wireless terminal and thelocation of the Packet Handling Subsystem assigned by the ATM ConnectionManagement Subsystem to handle the call, it sends a Reserve-channel orCommit-channel message, as appropriate, to the Radio Port ChannelManagement Subsystem to reserve or commit air-interface traffic channelresources and and the VP/VCs betweenthe radio port and the PacketHandling Subsystem. Note that it is preferred that the VC/VCs areprovisioned between the Packet Handling Subsystem and Radio PortSubsystem, and that during connection setup only a VCI on any of theseprovisioned VPSs needs to be picked in each direction.

2.3.5 Network Management Group of Subsystems

2.3.5.1 The Billing Subsystem

The Billing Subsystem preferably collects data from other subsystems(e.g., Call Management Subsystem and Multimedia Multiparty ManagementSubsystem) to track service usage for accounting purposes.

2.3.5.2 Security Subsystem

The duties of the Security Subsystem preferably include:

processing authentication-related information (e.g., AUTHR) appended toRegistration and Origination messages,

computing signaling message encryption keys, and

generating privacy masks (if applicable).

2.3.5.3 ATM Network Management Subsystem

The ATM Network Management Subsystem helps operate and maintain thebackbone portion of the network. This includes instances of the SpeechHandling Subsystem, the Call Management Subsystem, the ATM ConnectionManagement Subsystem, the Configuration and Location ManagementSubsystem and the Channel Management Subsystem. The ATM NetworkManagement Subsystem is not responsible for maintaining subsystemsunique to wireless access. The ATM Network Management Subsystem does notsupport, for example, the Radio Port or the Radio Port ChannelManagement Subsystem. As described in the next section, "wireless"domains are instead supported by the Wireless-Wired Gateway NetworkManagement Subsystem.

The ATM Network Management Subsystem performs performance monitoring,fault management and configuration management. It keeps track of changesin network topology. The ATM Network Management Subsystem determines thenumber and attributes of VP/VCs between Network Elements. It alsocomputes the routing tables used by the ATM Connection ManagementSubsystem to establish VP/VCs between network elements. In generatingthese tables the attributes of the connection as well as its endpointsare considered. The attributes include bandwidth, priority class, AALtype for VCCs to be carried within a VPS and explicit routinginformation (e.g., intermediate nodes). The ATM Connection ManagementSubsystem in turn uses this information to initialize translation tablesat cross-connects and ATM switches to provision the VP/VCs. The ATMNetwork Management Subsystem will also be responsible for computing anddownloading routing tables to the ATM Connection Management Subsystemfor use in establishing switched VP/VCs if and when the need for thesetypes of connections arises.

The data supporting ATM Network Management Subsystem fault andconfiguration management functions is derived from OA&M channelperformance measurements. When necessary, the ATM Network ManagementSubsystem and Wireless-Wired Gateway Network Management Subsystemscoordinate their activities via messages exchanged over pre-establishedVPCs. Communication of this sort is required, for example, to establishthe VPSs used to support new radio ports.

2.3.5.4 Wireless-Wired Gateway Network Management Subsystem

The Wireless-Wired Gateway Network Management Subsystem is preferablyresponsible for maintaining the portion of the network directlysupporting the wireless terminalenvironment. More specifically, it looksafter the OA&M needs of the Radio Port Subsystem, the Radio PortMultiplexing, the Packet Handling Subsystem, the Signaling MessageHandling Subsystem, the Control Channel Message Handling Subsystem, theRadio Port Channel Management Subsystem and the Wireless-Wired GatewayConnection Management Subsystem. Its duties preferably includeperformance monitoring, fault management and routing table computationand updating.

The latter function, routing table computation and updating, is invokedwhenever a component is added or removed from the network. When a radioport is added to the system, for example, it is the Wireless-WiredGateway Network Management Subsystem that assumes the responsibility forcreating the VPCs, VPSs, VCCs and VCSs used by the radio port tocommunicate with other network elements. This involves computing theoptimal route for each connection and sending provisioning messages tothe Wireless-Wired Gateway Connection Management Subsystem identifyingthe number of circuits to be added, their endpoints and attributes. Theattributes include bandwidth, priority treatment and, if needed,information on any intermediate nodes. If fast-hand-off procedures areto be supported, the Wireless-Wired Gateway Network Management Subsystemmust also coordinate the assignment of VP/VC identifiers for fasthand-off.

In addition to establishing the VPC/VCCs used to transport user data,the Wireless-Wired Gateway Network Management Subsystem is alsoresponsible for provisioning the dedicated VP/VCs used to carry accesschannel messages to the Control Channel Message Handling Subsystem,radio channel assignment data to radio ports, etc.

2.3.6 The Applications and Services Group of Subsystems

2.3.6.1 Speech Handling Subsystem

The Speech Handling Subsystem provides speech transcoding between thecompressed speech used over the air-interface and PCM used in the PSTN.Echo cancellation may also be implemented here.

2.3.6.2 Multimedia Multiparty Management Subsystem

The Multimedia Multiparty Management Subsystem provides service-specificprocessing to handle multimedia multiparty calls between user endpoints. It handles negotiations with user end-points to determine theirspecific characteristics. It then requests connections with bandwidthand Quality of Service attributes needed to meet the requirements of theservice. Requests for connections are conveyed to the ATM ConnectionManagement Subsystem via the Call Management Subsystem. This allows theCall Management Subsystem to perform additional feature management (ifrequired) before requesting connections from the ATM ConnectionManagement Subsystem. The Multimedia Multiparty Management Subsystemalso interacts with the Billing subsystem to track service usage foraccounting purposes.

2.6.3 Packet Data Handling Subsystem

The Packet Data Handling Subsystem terminates the AAL used at the PacketHandling Subsystem to support packet data. It also implements the linklayer and/or transport layer recovery procedures for packets transmittedand received over the air-interface and supports interworking with thepublic packet data network.

2.3.6.4 Circuit-Switched Data Handling Subsystem

The Circuit-Switched Data Handling Subsystem preferably implements linklayer functions and recovery strategies for the air-interface. Ifneeded, it also terminates the transport layer for the air-interface andinitiate a new one for the land network.

2.3.6.5 SS7 Message Handling Subsystem

The SS7 Message Handling Subsystem preferably terminates the MessageTransfer Part and Signaling Connection Control Part portions of the SS7protocol stack. Higher layer protocols are terminated elsewhere in thesystem. The ISDN User Part and the IS-41 Mobile Application Partprotocols, for example, are terminated by functions in the CallManagement Subsystem.

2.3.6.6 Fax Handling Subsystem

The Fax Handling Subsystem functions in essentially the same way as thePacket and Circuit-Switched Data Handling subsystems. That is, itterminates air-interface link layer functions, supports there-establishment of failed links and provides any interworking with theland network needed to establish and maintain the end-to-end transfer ofdata.

2.3.6.7 Message Services Subsystem

This Subsystem is responsible for any service-specific processingassociated with the handling and delivery of e-mail, voice-mail, shortmessage service and paging traffic.

2.3.6.8 Video Services Subsystem

The Video Services Subsystem is responsible for the processingassociated specifically with video services, in all its forms. Severaldifferent subsystems may be established for different types of video andimage services.

3. Pedagogical Scenarios

This section discusses three typical call scenarios from the perspectiveof message flow. This facilitates an understanding of the interactionbetween subsystems during registrations and call setups. It should beunderstood that the message flows and/or primitive exchanges describedin this section are between subsystems and can be, but are notnecessarily, between hardware platforms.

3.1 Registration at Power Up

The flow of information during a typical power-up registration isillustrated in FIG. 6. When a wireless terminal is turned on, it locatesand locks onto a paging channel. Once synchronized, it begins to acquiresystem parameters. Of particular interest here is the parameterindicating whether or not power-up registration is required. If it is,the wireless terminal generates a Registration message and sends it tothe radio port via the access channel. The radio port forwards theRegistration message to the Control Channel Message Handling Subsystemover a pre-established VP/VC. The Registration message contains the MIN,ESN, user-specific data, together with information used by the mediaaccess control ("MAC") algorithms of the access channel. Theuser-specific data includes the value of the MOB₋₋ TERM parameterindicating the willingness of the subscriber to accept incoming calls.Other user-specific data (e.g., mobility indexes, terminal capabilites)may be included in the Registration message in the future.

The Control Channel Message Handling Subsystem processes theRegistration message and invokes a MOB₋₋ REG operation in the servingConfiguration and Location Management Subsystem. The MOB₋₋ REGinvocation contains the MIN, ESN, user-specific data, and the identityof the Control Channel Message Handling Subsystem able to communicatewith the wireless terminal. The serving Configuration and LocationManagement Subsystem processes the MOB₋₋ REG invocation and assigns aUser Signaling Server Subsystem, ATM Connection Management Subsystem andWireless-Wired Gateway Connection Management Subsystem. The servingConfiguration and Location Management Subsystem initiates a User Processon the User Signaling Server Subsystem it selected via an INST₋₋ USER₋₋PROCESS invocation. This invocation contains the user-specific dataincluded in the MOB₋₋ REG invocation. If the wireless terminal is in itshome network and is in one of its predesignated zones, the invocationalso includes a list of zones which are to be maintained in the wirelessterminal's zone list, and a list of Control Channel Message HandlingSubsystems that are associated with the zones on the list. If thewireless terminal is not in its home system, or is in its home systembut not in one of its predesignated zones, the INST₋₋ USER₋₋ PROCESSinvocation only includes a list of the Control Channel Message HandlingSubsystems associated with the zone in which the user currently islocated.

A Call Management Subsystem is assigned to the wireless terminal oncethe User Process has been initiated. Two cases are considered here. Thefirst pertains to wireless terminals operating in their home system. Inthis case, the serving Configuration and Location Management Subsystemuses the Call Management Subsystem assigned to the user when it wasactivated. If, in constrast, the wireless terminal is not in its homesystem, the serving Configuration and Location Management Subsystemidentifies the wireless terminal's Home-Configuration and LocationManagement Subsystem ("H₋₋ Configuration and Location ManagementSubsystem") from its MIN and sends it a MOB₋₋ REG message. Theinvocation includes the wireless terminal's MIN together with thelocation of the User Process and is delivered via a pre-establishedsignaling VP/VC. Note that User Signaling Server Subsystems havepre-established VP/VCs to the gateway Configuration and LocationManagement Subsystems of all systems with which the serving system has abusiness arrangement. FIG. 6 illustrates the case in which the wirelessterminal is not in its home system.

After this phase of the registration process is complete, theConfiguration and Location Management Subsystems in both networks updateother subsystems within their networks via a series of UPDATE messages.In the serving network, for example, the Configuration and LocationManagement Subsystem contacts all of the Control Channel MessageHandling Subsystems in the zone in which the wireless terminal iscurrently located, informing them in particular of the address of theUser Process serving the wireless terminal. If the wireless terminalregistered in one of its predesignated zones in its home network, thenall of the Control Channel Message Handling Subsystems associated withall the zones in the wireless terminal's zone list are updated. This isrequired so that the Control Channel Message Handling Subsystem canforward subsequent Registration messages as well as Origination messagesdirectly to the User Process.

The serving Configuration and Location Management Subsystem also updatesthe serving ATM Connection Management Subsystem with the address of theWireless-Wired Gateway Connection Management Subsystem assigned thewireless terminal. This is done to ensure that the ATM ConnectionManagement Subsystem contacts the correct Wireless-Wired GatewayConnection Management Subsystem if and when it becomes necessary toestablish a connection between the wireless terminal and the landnetwork. Finally, the serving Configuration and Location ManagementSubsystem preferably updates the Wireless-Wired Gateway ConnectionManagement Subsystem with the MIN and ESN of the wireless terminal, aswell as the location of its User Process. The Wireless-Wired GatewayConnection Management Subsystem uses the User Process locationinformation as described in Sections 3.2 and 3.3 to establish the PacketHandling Subsystem to radio port portion of a connection.

In the home network, the Configuration and Location Management Subsystemupdates the Call Management Subsystem with the MIN and User Processlocation. The Call Management Subsystem needs to know the location ofthe User Process so that it can contact the User Process with call orservice requests. Once updated, the Call Management Subsystem contactsthe User Process directly with a SIGNALING₋₋ WAKEUP invocation to informthe User Process that it now has an active signaling link with a CallManagement Subsystem. The wireless terminal is fully registered at thispoint.

3.2 Wireless Terminal Originated Calls

The information flow for a wireless terminal originated call is shown inFIG. 7. In this example we consider the case in which a Speech HandlingSubsystem is needed to convert compressed speech from the air interfaceto 64 Kbps PCM. We also assume that the wireless terminal is not in itshome system.

The process starts when the wireless terminal generates an Originationmessage and sends it to the serving radio port on the reverse control(access channel). The radio port forwards the message to the ControlChannel Message Handling Subsystem which, in turn, informs the UserProcess of the wireless terminal's desire to obtain service by sendingit a MOB₋₋ ORIG message. The MOB₋₋ ORIG message contains the wirelessterminal's identity as well as the identity of the radio port thewireless terminal accessed. The User Process processes the MOB₋₋ ORIGinvocation and invokes a SETUP₋₋ CALL operation in the wirelessterminal's Call Management Subsystem. This invocation includes theidentity of the called party and an embedded request for a connection tothe called party.

The wireless terminal's Call Management Subsystem then contacts thecalled party's Call Management Subsystem with a SETUP₋₋ CALL message todetermine whether or not the called party is willing to accept the call.In parallel, the wireless terminal's Call Management Subsystem queriesits H-Configuration and Location Management Subsystem to determine theATM Connection Management Subsystem best able to handle the call. To dothis, the H₋₋ Configuration and Location Management Subsystem contactsthe serving Configuration and Location Management Subsystem with a FIND(ATM Connection Management Subsystem) message. The H₋₋ Configuration andLocation Management Subsystem forwards the information in theConfiguration and Location Management Subsystem's response the wirelessterminal's Call Management Subsystem. When the Call Management Subsystemreceives a positive response from the called party's Call ManagementSubsystem indicating that the called party is willing to accept the calland the identity of the ATM Connection Management Subsystem in theserving network has been established, the connection establishment phaseis entered. Note that for wireless terminals operating in their homesystems there is no distinction between Home and serving Configurationand Location Management Subsystems.

The connection establishment phase commences with the Call ManagementSubsystem invoking a a SETUP₋₋ CONNECTION operation in the serving ATMConnection Management Subsystem. The invocation includes the MIN of thecalling party and the address of the called party. The serving ATMConnection Management Subsystem associates the MIN of the calling partywith a Wireless-Wired Gateway Connection Management Subsystem and sendsit a SETUP₋₋ CONNECTION message. The invocation includes the MIN of thecalling party. In parallel, the serving ATM Connection ManagementSubsystem routes a segment from the point-of-presence of the landnetwork to the Speech Handling Subsystem assigned by the serving ATMConnection Management Subsystem to handle the call. The serving ATMConnection Management Subsystem also invokes a SETUP₋₋ SEGMENT operationin the land network ATM Connection Management Subsystem serving thepoint-of-presence requesting that it establish a segment between thepoint-of-presence and the called party.

As discussed above, the Wireless-Wired Gateway Connection ManagementSubsystem is responsible for establishing the portion of the connectionbetween the radio port serving the wireless terminal and the PacketHandling Subsystem. This amounts to selecting one of the pre-establishedVPS/VCSs. To determine the radio port best able to handle the call, theWireless-Wired Gateway Connection Management Subsystem queries the UserProcess with a FIND(radio port) message. When it receives a response,the Wireless-Wired Gateway Connection Management Subsystem commands boththe Radio Port Channel Management Subsystem associated with the radioport and the ATM Channel Management Subsystem supporting the PacketHandling Subsystem assigned by the Wireless-Wired Gateway ConnectionManagement Subsystem to handle the call, to reserve and commit channels.This effectively establishes a connection between the wireless terminaland the Packet Handling Subsystem. The Wireless-Wired Gateway ConnectionManagement Subsystem then responds to the SETUP₋₋ CONNECTION requestfrom the serving ATM Connection Management Subsystem, informing it thata connection terminating on the Packet Handling Subsystem identified inthe response has been established. At this time the Wireless-WiredGateway Connection Management Subsystem updates the User Process andSignaling Message Handling Subsystem (normally co-located with thePacket Handling Subsystem) as to each others location so that they mayexchange in-call signaling messages.

The serving ATM Connection Management Subsystem then establishes aconnection between the Speech Handling Subsystem and the Packet HandlingSubsystem. Recall that the serving ATM Connection Management Subsystemhas already committed channels from the point-of-presence to the SpeechHandling Subsystem. This is done by reserving and committing channelsfrom the Speech Handling Subsystem to the Packet Handling Subsystem,through perhaps one (or several) ATM switch(s).

Once the ATM Connection Management Subsystem in the land network hascompleted establishing its segment, an end-to-end connection exists. Theend-to-end connection consists of a connection between the land terminaland the Speech Handling Subsystem, a connection between the SpeechHandling Subsystem and a Packet Handling Subsystem, and a connectionbetween the Packet Handling Subsystem and the radio port. Once theserving ATM Connection Management Subsystem ascertains that theend-to-end connection does in fact exist, it notifies the Wireless-WiredGateway Connection Management Subsystem which, in turn, invokes aSETUP₋₋ VCC₋₋ ENDPOINT operation in the Signaling Message HandlingSubsystem. The Signaling Message Handling Subsystem translates thisoperation into an Alert With Information message which is sent to thewireless terminal on the traffic channel. This initiates ring-back inthe wireless terminal and, optionally, instructs the wireless terminalhow to map an incoming channel with a connection request. The latter isrequired when a wireless terminal has multiple active connections.

3.3 Wireless Terminal Terminated Calls

The flow of information during the establishment of a wireless terminalterminated call is depicted in FIG. 8. Once again it is assumed that aSpeech Handling Subsystem is required and that the wireless terminal isnot in its home system. For our purposes, the process begins when theCall Management Subsystem of the calling party contacts the wirelessterminal's Call Management Subsystem, requesting it to invoke anyimplicit services activated by the wireless terminal subscriber. Thewireless terminal's Call Management Subsystem offers the call directlyto the User Process via an OFFER₋₋ CALL message.

The User Process replies positively to this request, indicating that itcan accept the call. In parallel, the Call Management Subsystem for thecalling party queries the wireless terminal's H₋₋ Configuration andLocation Management Subsystem to determine the ATM Connection ManagementSubsystem to be used by the serving system to service the call and thepoint-of-presence through which connections to the wireless terminal areto be routed. The H₋₋ Configuration and Location Management Subsystemdoes not store this information locally and thus queries the servingConfiguration and Location Management Subsystem. This is done via a FIND(ATM Connection Management Subsystem) message.

When the serving Configuration and Location Management Subsystem repliesto this message, the H₋₋ Configuration and Location Management Subsystemin turn replies to the request of the calling party's Call ManagementSubsystem. When the Call Management Subsystem serving the calling partyhas also received an indication that the call has been accepted the callphase is considered complete.

The connection phase commences when the ATM Connection ManagementSubsystem serving the calling party network invokes a SETUP₋₋ SEGMENToperation in the ATM Connection Management Subsystem serving thewireless terminal. The SETUP₋₋ SEGMENT message contains the MIN of thecalled party and the point-of-presence through which the connection mustbe routed. The ATM Connection Management Subsystem serving the wirelessterminal associates the MIN with a Wireless-Wired Gateway ConnectionManagement Subsystem and invokes within it a SETUP CONNECTION operation.In the mean time, the ATM Connection Management Subsystem serving thewireless terminal routes a segment from the point-of-presence to aSpeech Handling Subsystem.

The Wireless-Wired Gateway Connection Management Subsystem associatesthe MIN with a User Process and queries the User Process to find theradio port able to communicate with the wireless terminal. This is donevia a FIND (radio port) message. The User Process does not have thisinformation stored locally and thus pages the wireless terminal. Thepaging process is carried out via the Control Channel Message HandlingSubsystems in the area where the wireless terminal last registered. Whenthe wireless terminal responds to the page, the Control Channel MessageHandling Subsystem processing the response forwards the identity of theradio port that received it to the User Process. The User Process inturn reports the identity of the radio port to the Wireless-WiredGateway Connection Management Subsystem.

The Wireless-Wired Gateway Connection Management Subsystem theninstructs the Radio Port Channel Management Subsystem and the ATMChannel Management Subsystem supporting the Packet Handling Subsystemassigned to handle the call to reserve and commit a channel between theradio port and the Packet Handling Subsystem. This effectivelyestablishes a connection from the wireless terminal to the PacketHandling Subsystem. The Wireless-Wired Gateway Connection ManagementSubsystem then replies to the SETUP₋₋ CONNECTION request from the ATMConnection Management Subsystem serving the wireless terminal. Once theATM Connection Management Subsystem serving the wireless terminal knowsthe location of the Packet Handling Subsystem assigned by theWireless-Wired Gateway Connection Management Subsystem to handle thecall it establishes a connection between the Speech Handling Subsystemand Packet Handling Subsystem. This is done by sending a RESERVE&COMMITmessage to the ATM Channel Management Subsystems supporting them. Atthis point the ATM Connection Management Subsystem serving the wirelessterminal replies to the SETUP₋₋ SEGMENT message sent by the ATMConnection Management Subsystem serving the calling party at the startthe connection establishment phase.

When the end-to-end connection has been established, the ATM ConnectionManagement Subsystem serving the calling party sends a CONN₋₋ ESTmessage to the ATM Connection Management Subsystem serving the wirelessterminal, which in turn passes it on to the Wireless-Wired GatewayConnection Management Subsystem. The Wireless-Wired Gateway ConnectionManagement Subsystem invokes a SETUP₋₋ VCC₋₋ ENDPOINT operation in theSignaling Message Handling Subsystem to establish the mapping betweenthe connection and a specific service request. The Signaling MessageHandling Subsystem translates this invocation into an Alert WithInformation message which is sent to the user on the traffic channel toinstruct the wireless terminal to alert the subscriber. When the useranswers, a Connect order is sent to the radio port on the reversetraffic channel. The Packet Handling Subsystem serving the radio portroutes this message to the Signaling Message Handling Subsystem, whichcompletes the process by sending a SETUP₋₋ VCC₋₋ SEGMENT.RSP message tothe Wireless-Wired Gateway Connection Management Subsystem.

4. Network Elements

The material in this section describes how the subsystems described inSection 2 are preferably grouped into network elements in accordancewith the exemplary embodiment. As illustrated in FIG. 9, eight unitsare:

RF Distribution Unit 901;

Packet Processing Complex 903;

Narrowband Interworking Unit 905;

ATM Switch 907;

Wireless Control Complex 911;

Wired Network Control Complex 913

Application Server Complex 915; and

Network Management 917

4.1 RF Distribution Unit

RF Distribution Unit 901 preferably comprises: radio ports, radio portmultiplexors and "landline" facilities. Radio ports and radio portmultiplexors may be arranged in tree, ring or mesh configurations, asdictated by cost and reliability targets as well as the availability offacilities.

A block diagram of a typical radio port is given in FIG. 10. Note that aone-to-one correspondence between the individual functional blocks andphysical processors is neither implied nor warranted, although thelimitations of available technology or requirements such as the abilityto support a variety of air-interfaces and/or digital facilitiesinterfaces might lead to such a design. FIGS. 20, 21 and 22 depicttypical configurations for the RF Distribution Network.

4.2 Packet Processing Complex

As depicted in FIG. 11, Packet Processing Complex 903 preferablycomprises: one or more packet handlers 1103, which separate signalingfrom voice, one or more signal message handlers 1111 to terminate theair interface signaling protocol, one or more radio channel managers1105, which process radio channel quality data from the wirelessterminals and/or the radio port, ATM channel manager 1109, whichhandlers VP/VC translation tables at the network elements, and switch1101, all interconnected as shown. Depending on the particularapplication, switch 1101 could be a LAN, microswitch or macroswitch. Inany case, all but the smallest of systems would likely have multiplepacket processing complexes, each serving several radio ports. For verysmall systems a single hardware platform housing this functional blockmight suffice.

4.3 Narrowband Interworking Unit

The preferred role of Narrowband Interworking Unit 905 is to convert thelow bit rate coded speech carried throughout the wireless network andacross the air-interface into a form compatible with the narrowband landnetwork (e.g., PSTN). To this end, as illustrated in FIG. 12, NetworkInterface Unit 905 preferably comprises: one or more speech handlers1203, which perform speech transcoding, ATM channel changer 1205, whichhandles VP/VC translation tables, one or more facilities interface 1207,which terminates digital facilities, narrowband switch 1209, whichinterfaces to the narrowband network and switch 1201, all interconnectedas shown. Depending on the particular application, switch 1201 could bea LAN, microswitch or macroswitch. It is preferred that hardwareplatforms supporting Narrowband Interworking blocks will be located asclose as possible to narrowband network interface points so as tomaximize the savings associated with transporting compressed speech andto minimize access charges.

4.4 ATM Switch

ATM Switch 907 is preferably an off-the-shelf ATM switch, which isavailable from several manufacturers. The features normally associatedwith contemporary switches, e.g., AT&T's 5ESS® switch, areadvantageously moved to Wired Network Control Complex 913 andApplication Server Complex 915. This not only enables the architectureto be scalable, but also facilitates the development and introduction ofnew features in a multi-vendor environment. Note that it is notnecessary that ATM Switch 907 can support both wireless and wirelineservices.

4.5 Wireless Control Complex

As shown in FIG. 13, Wireless Control Complex 911 preferably comprises:one or more Control Channel Message Handlers 1301, one or moreWireless-Wired Gateway Connection Managers 1305, one or more Radio PortChannel Managers 1307, one or more User Process/User Signaling Servers1309, ATM Channel Manager 1311 and switch 1301, all interconnected asshown.

The Control Channel Message Handlers 1301 are preferably the embodimentof the Control Channel Message Handling Subsystem and act as signalingfixed-points for wireless terminals that are active in the system butnot engaged in a call. The Wireless-Wired Gateway Connection Mangers1305 are preferably the embodiment of the Wireless-Wired GatewayConnection Management Subsystem and establish the routes betweenwireless network elements such as Speech Handlers 1203 and the PacketHandlers 1103.

The Radio Port Channel Managers 1307 are preferably the embodiment ofthe Radio Port Channel Management Subsystem and manage RF resources andact as ATM channel managers for the radio ports they support. The UserProcess/User Signaling Servers 1309 are preferably the embodiment of theUser Signaling Server Subsystem and represent wireless terminals innegotiations with the network concerning the service(s) to be provided.Depending on the particular application, switch 1301 could be a LAN,microswitch or macroswitch. The ATM Channel Manager 1311 handles theVP/CP translates tables for the Wireless Control Complex.

It is preferred that each Wireless Control Complex 911 preferablysupport multiple RF Distribution Units, Packet Processing Complexes andNarrowband Interworking Units.

4.6 Wired Network Control Complex

As shown in FIG. 14, Wired Network Control Complex 913 preferablycomprises: one or more Call Managers 1403, one or more SS7 MessageHandlers 1405 (and associated SS7 Signaling Transport Point 1407),Billing Handler 1409, Configuration and Location Manager 1411,Connection Manager 1413, ATM Channel Manager 1415, AuthenticationHandler 1417 and switch 1401, interconnected as shown.

Call Managers 1403 preferably embody the Call Management Subsystem, SS7Message Handlers 1405 preferably embody the SS7 Message HandlingSubsystem, SS7 Signaling Transport Point, Billing Handler 1409preferably embodies the Billing Subsystem, Configuration and LocationManager 1411 preferably embodies the Configuration and LocationManagement Subsystem, Connection Manager 1413 preferably embodies theConnection Management Subsystem, ATM Channel Manager 1415 preferablyembodies the ATM Channel Managment Subsystem and Authentication Handler1417 preferably embodies the Security Subsystem. Depending on theparticular application, switch 1401 could be a LAN, microswitch ormacroswitch.

From a functional perspective, Wired Network Control Complex 913preferably provides:

call processing;

the allocation of wireless network control resources with the help ofthe Configuration and Location Management Subsystem:

network-level routing with the ATM Connection Management Subsystem;

the generation of billing records with the Billing subsystem;

subscriber and/or wireless terminal authentication with the SecuritySubsystem; and

interfaces to signaling networks such as SS7 via specialized handlersthat terminate physical, link and possibly network and transport layers.

Because typical embodiments of the present invention are likely tocomprise only one Wired Network Control Complex, it is preferred thatparticular attention be paid to the reliability aspects of prospectiveplatforms supporting this complex.

4.7 Application Server Complex

Application Server Complex 915 enjoys the same level of abstraction inthe architecture as the Wired Network Control Complex 913, but, as thename suggests, the functions provided by Application Server Complex 915are service-specific in contrast to those in the Wired Network ControlComplex 913, which tend to be more generic. Referring to FIG. 15,Application Server Complex 915 preferably comprises one or moreMultimedia Multiparty Managers 1503 (which preferably embody theMultimedia Mulitparty Management Subsystem), Video Server 1505 (whichpreferably embodies the Video Service Subsystem), ATM Channel Manager1507, CDPD Handler 1509 and Data Handler 1513 (which together embody thePacket Data Handling Subsystem), Message Service Handler 1511 (whichembodies the Message Services Subsystem), Fax Handler 1515 (whichembodies the Fax Handling Subsystem), and switch 1501, allinterconnected as shown. Depending on the particular application, switch1501 could be a LAN, microswitch or macroswitch.

Note that the call processing associated with a given application can bemoved from Application Server Complex 915 to Call Managers 1403 in WiredNetwork Control Complex 913 when the service "matures" or if performancebecomes an issue.

4.8 Network Management Complex

Referring to FIG. 16, Network Management Complex 917 preferablycomprises: Wireless-Wired Gateway Network Manager 1603 (which preferablyembodies the Wireless-Wired Gateway Network Management Subsystem), ATMNetwork Manager 1605 (which preferably embodies the ATM NetworkManagement Subsystem), ATM Channel Manager 1607, and ATM switch 1601,all interconnected as shown. Depending on the particular application,switch 1601 could be a LAN, microswitch or macroswitch.

5. Hand-Off Management

Hand-Off is a process of changing the route of information flow toand/or from the wireless terminal to a fixed point (e.g., a radio port)to enhance the quality of information transport, or to avoid degradationof information transport quality resulting from mobility or changes ininterference patterns. Additionally, spread spectrum based airinterfaces (e.g., CDMA) enable multiple routes between the wirelessterminal and a fixed point in the network to coexist simultaneously forthe purpose of providing a better information transport quality thanpossible on any one route alone.

A "hard hand-off" is a hand-off that sets up a new route and almostconcurrently tears down the old route. When a hand-off adds a new routewithout almost concurrently tearing down the old route, it can be"soft," "softer," or a "semi-soft." A "softer hand-off" involved twosectors of the same radio port. When diversity routes involve differentradio ports, a common Frame Selector selects the best quality frame fromamong those arriving over diverse routes.

In the exemplary embodiment, the Frame Selector (not shown) is part ofPacket Handler 1103. Furthermore, in the exemplary embodiment, eachPacket Handler (with associated Frame Selector) preferably supportsmultiple radio ports through radio port multiplexors. This isadvantageous because it enables each Packet Handler to be the fixedpoint for a collection of radio ports. When a Packet Handler is thefixed point for a collection of radio ports, each radio port in thecollection is said to be "associated" with the Packet Handler.

ATM network 907 enables any radio port in RF Distribution Unit 901 toreach any Packet Handler 1103, whether or not the radio port isassociated with that Packet Handler.

When the new and old routes of a hand-off involve radio ports that areall associated with a single Packet Handler, then a "fast hand-off" isadvantageously enabled, which will be discussed in detail below. On theother hand, when the new and old routes of a hand-off involve radioports that are associated with more than one Packet Handler, and therespective Packet Handlers are reached by the respective radio ports viadifferent ATM switches, then a "slow hand-off" advantageously occurs,which will be discussed in detail below.

Wireless access technologies that do not use diverse air routes (e.g.,AMPS, IS-54 TDMA) in contrast to those that do (e.g., IS-95 CDMA)preferably employ "hard hand-offs." A hard hand-off can be, in addition,characterized as either fast or slow. Wireless access technologies thatdo use diverse air routes (e.g., IS-95 CDMA) preferably employ "softhand-offs" through the use of a Frame Selector (and associated PacketHandler). A soft hand-off can be, in addition, characterized as eitherfast or slow depending on whether the germane radio ports share a commonPacket Handler. Hard hand-offs are additionally advantageously used incases when there is a resource shortage and when the hand-off involvesdifferent access technologies (e.g., CDMA and AMPS).

The exemplary embodiment supports hard hand-offs (both fast and slow)and soft hand-offs (both fast and slow). The exemplary embodimentadvantageously uses the advantages of ATM technology to enable hand-offswhich are truly fast. In the exemplary embodiment, this is accomplishedby either completely or partly pre-establishing the VP/VCs between agiven Packet Handler and all of its associated radio ports (and radioport multiplexors and by only activating those resources that areactually needed at a given time. In the exemplary embodiment, thewireless terminal is provided with information during call set-up sothat the wireless terminal can use this information to facilitateexpedited activation and authentication over the new route. As will bediscussed in greater detail below, it is preferred that the wirelessterminal be given a matched set of VP/VCs, which the wireless terminalgives to a radio port with which the wireless terminal desires toestablish a new route.

Because there is a limitation on the number space of VP/VCs and becauselarge routing tables, which are technically advantageous, may beeconomically prohibitive in certain cases, the exemplary embodimentpreferably also supports slow hand-offs. Fortunately, the exemplaryembodiment enables even "slow" hand-offs to be completed relativelyquickly through the use of partially pre-established VP/VCs.

Another aspect of hand-off management involves detecting thedesirability of a hand-off. The decision of whether or not to hand-off,and if so, how, can involve numerous factors and perspectives. This isaddressed in Section 5.1. The exemplary embodiment preferably useswireless terminal directed hand-off, which is discussed in detail inSection 5.2. Section 5.3 describes techniques for expedited hand-offsusing ATM VP/VCs. It should be understood that each of the techniquetaught in Section 5.3 can be used with any hand-off direction technique.

5.1 Hand-Off Direction

In accordance with the IS-54 TDMA, IS-95 CDMA and GSM air interfaces,hand-offs are both initiated and directed by the network with theassistance of the wireless terminal, which assistance is in the form ofForward Channel quality measurements for neighboring base stations. Ingeneral, network initiated and directed hand-offs have been favoredbecause it enables inexpensive wireless terminals, and because itfacilitates authentication of the wireless terminal.

5.1.1 Network Directed Hand-Off

Although it is not preferred, the exemplary embodiment can supportnetwork initiated and directed hand-offs as follows. Radio ChannelQuality Managers 1105 periodically supplies every active (in call)wireless terminal with a list of Neighbor Radio Ports. This informationcan be sent to the wireless terminal as signaling information via theSignaling Message Handler/Packet Handler and the radio port (or radioports) currently serving the wireless terminal. The wireless terminalthen collects measurements on the Pilot Channel or Forward ControlChannel quality for the Neighbor Radio Ports and sends them back to theRadio Channel Quality Manager.

The Radio Channel Quality Manager can take the data from the wirelessterminal, and use the Forward Channel quality and Reverse Channelquality measurements for the current radio port and decide if a hand-offis desirable and, if it is, which radio port (among the Neighbor RadioPorts) should be deemed the Target Radio Port.

The Radio Channel Quality Manager can then send a message to the TargetRadio Port requesting a hand-off and supplying information to affectconnections from the Target Radio Port to the wireless terminal and tothe associated Packet Handler. If the Target Radio Port does not havesufficient resources or it finds the Reverse Channel Quality (which itcan collect only after locking on to the wireless terminal)unacceptable, the Target Radio Port may deny the hand-off request. TheRadio Channel Quality Manager can then try an alternate Target RadioPort or deny hand-off altogether. For the following reasons, networkdirected hand-off is not preferred in the exemplary embodiment.

As the number of wireless terminals increases, and as radio ports areoperated in closer proximity to each other, the density of radio portsper unit area increase and with it the amount processing required by theRadio Channel Quality Manager. Another militating factor is that as theradio port density increases, the Reverse Channel will be required tocarry more Forward Channel quality measurement data.

Furthermore, in a hybrid environment comprising both macro andmicrocells, the decision of whether to allocate new calls to macro ormicrocells must be based on the mobility behavior of the wirelessterminal is considered. It is suggested that it is economicallyprohibitive for the Radio Channel Quality Manager to monitor themovement of both active and idle wireless terminals for such purposes.The mobility of the wireless terminal is best monitored by each wirelessterminal itself.

5.1.2 Wireless Terminal Directed Hand-Off

The exemplary embodiment of the present invention preferably supportswireless terminal directed hand-off, even though this requires thewireless terminal to be somewhat more complex.

In particular, although with network directed hand-off the wirelessterminal merely transmits the channel quality measurements it waspreviously collecting, with wireless terminal directed hand-off thewireless terminal must be capable of negotiating a hand-off with aTarget Radio Port while simultaneously supporting duplex communicationwith the original radio port(s). To this end, Section 5.2 describeswireless terminal directed hand-off as supported by the exemplaryembodiment of the present invention.

We assume that the Radio Port Channel Manager periodically evaluates thestatus of each radio port it is controlling. This may include loadingstatus (number of calls being handled, etc.) as well as any otherfactors which may affect the desirability of adding a new call or ahand-off to that radio port. Also, the Radio Port Channel Managermaintains, for each radio port, a relatively static list of NeighborRadio ports (NL). Based on the periodic evaluation of radio port status,Radio Port Channel Manager creates a trimmed (or prioritized) list ofCurrent Neighbors (CNL) for each radio port. The CNL is thus aprioritized list of Radio ports ready to accept a new call or a hand-offif the Reverse Channel Quality is acceptable. This list is sent orbroadcast to the wireless terminalperiodically based on the currentradio port being used. The actual content will include at least thePilot Channel for every radio port in CNL and may include the NeighborAccess Channels and Forward Control Channels as well. The trimming orprioritizing the NL to CNL implies a lower probability of a hand-offrequest failure due to resource unavailability.

An alternative to providing the CNL periodically is for the Radio PortChannel Manager to request every radio port to broadcast a radio portspecific dynamic threshold periodically over the air interface. Thesethresholds are used by the wireless terminal to decide if the ForwardChannel Quality for a given radio port is acceptable. By choosing thethreshold high for heavily loaded Radio ports the Radio Port ChannelManager indirectly informs the wireless terminal of the loading statusof Radio ports. This has the advantage of providing finer granularityover the previously described CNL but makes the wireless terminaloperation more complex. Another alternative is to adjust the PilotChannel power to reflect the loading on an radio port (in effect,dynamically changing the coverage area). We have chosen the firstapproach in our proposal because it keeps the wireless terminaloperations simple.

5.1.3 Authentication in a Wireless Terminal Directed Hand-OffEnvironment

When the exemplary embodiment supports wireless terminal directedhand-off, it is preferred that wireless terminal authentication beprovided as follows. Because standard authentications take a significantamount of time, the goal of a fast hand-off is frustrated if thewireless terminal must go through the standard authentication procedureeach time it requests a hand-off. Therefore, it is preferred that thewireless terminal go through the standard authentication process duringcall set-up, and thereafter, engage in an expedited well-knownchallenge-response exchange with the new Packet Handler to affectauthentication without delaying the hand-off.

5.2 Procedure for Wireless Terminal Directed Hand-Off: Messaging Details

This section discusses the procedure and associated timing associatedwith wireless terminal directed hand-off using preestablished VP/VCsbetween radio ports and Packet Handler 1103, as supported by theexemplary embodiment. Resources are allocated to these pre-establishedVP/VCs only at hand-off. The procedures involving connectionestablishment at the time of hand-off (i.e., no preestablished VCCs) aresimilar.

As described earlier, using the Radio Port Neighbor list andcorresponding measurements the wireless terminal initiates hand-off to aTarget Radio Port. Initiation of hand-off by the wireless terminal isaccomplished by sending a handoff₋₋ request message on the accesschannel of the Target Radio Port and including the ID of the PacketHandler (typically represented by VP/VC identifiers that uniquelyidentify the Packet Handler) to which it is currently connected, so thatthe radio port can determine whether a fast hand-off is possible. Thehandoff₋₋ request includes the information required for the radio portand Packet Handler to complete a fast hand-off if the radio port isassociated with the Packet Handler which is currently carrying the call.Also included in the handoff₋₋ request is information (e.g., thewireless terminal's ESN) that the Target Radio Port will need in orderto decode the mobile's packets (e.g., CDMA packets) if it were to acceptthe handoff₋₋ request. If the Target Radio Port has no resourcesavailable it can reject the hand-off request by transmitting a handoff₋₋reject message to the wireless terminal on the Forward Control Channel(Paging Channel) of the Target radio port.

The remainder of this section describes three hand-off scenarios indetail that the exemplary embodiment can support. Section 5.2.1describes a scenario in which the wireless terminal is allotted 3 VCidentifiers at call set-up and provides one that is not in use to theTarget Radio Port as part of the handoff₋₋ request message. Preferablyradio ports that are associated with the Packet Handler serving thewireless terminal have pre-established VCs to the Packet Handler. Thegermane message flows associated with this scenario are depicted in FIG.17.

Section 5.2.2 describes the second scenario where pre-established VPsbetween the Packet Handler and the associated Radio ports are used. VCsare picked at the time of hand-off. The germane message flows associatedwith this scenario are depicted in FIG. 18. Section 5.2.3 describes thethird scenario in which a complete VP/VC establishment from the PacketHandler to the Target radio port is required at hand-off because theTarget radio port is not associated with the Packet Handler (or when thesystem does not support fast hand-offs. The germane message flowsassociated with this scenario are depicted in FIG. 19.

5.2.1 Pre-established Unidirectional VCCs

When pre-established uni-directional VCCs are used between a radio portand its associated Packet Handler, the wireless terminal provides theVCI (that is pre-established to the Packet Handler in the uplinkdirection), in the handoff₋₋ request message. FIG. 17 depicts the timingof the germane message flows for an example of successful hand-off eventdirected by the wireless terminal for this scenario. The Target RadioPort attaches the VCI it received from the accessing wireless terminaland sends a set₋₋ reverse₋₋ VC message in a signaling OA&M cell to theradio port multiplexer which routes the OA&M ATM cell to the PacketHandler over the pre-established uni-directional VC connection. ATMtechnology in particular describes the use of OA&M cells that areintercepted at intermediate network nodes for OA&M purposes. We describea novel use of these OA&M cells for facilitating fast hand-off.

The OA&M cell is read by the intermediate switches and multiplexersbefore being forwarded to the next entity on the pre-established VCconnection. The downlink VC connection establishment is through the ATMrouting controller table at each switch or radio port multiplexer, whichmaps an outgoing downlink VC identifier to each incoming port andincoming VC identifier on the uplink. Resource unavailability on anylink and/or processor on this route will result in the rejection of therouting request. In that case, a handoff₋₋ reject message is sent backto the Target Radio Port and then via the Radio Port Channel Manager andControl Channel Message Handler to the wireless terminals.

If resources are available along the entire route, then the hand-offrequest can be accepted, and the downlink VC identifiers established asthe set₋₋ reverse₋₋ VC OA&M cell traverses the pre-established uplinkVCC. At this point an ack₋₋ VC OA&M cell is transmitted on the newlyestablished downlink VCC to the radio port. The Radio Port ChannelManager is informed of the establishment of the required duplex VCCbetween the radio port and the Packet Handler. The Radio Port ChannelManager can now assign a radio channel to the hand-off call and informthe wireless terminal of the acceptance of the handoff₋₋ request using ahandoff₋₋ direction message. The handoff₋₋ direction message to thewireless terminal includes voice channel assignment (e.g., WalshFunction in CDMA) information that the wireless terminal uses to decodepackets transmitted by the Target Radio Port. This message istransmitted on the Forward Control Channel of the Target Radio Port.After the wireless terminals and the radio port are synchronized on thenew Radio Channel, the wireless terminal transmits a handoff₋₋ completemessage to the radio port, which is forwarded for information to theWireless-Wired Gateway Control Manager.

This method results in a "very" fast soft or hard hand-off processwhereby no delay is incurred in the uplink direction for connectionestablishment. The downlink VCC is established while the first ATM OA&Mcell is transmitted to the Packet Handler. 5.2.2 Pre-establishedBi-directional VPCs

FIG. 18 depicts the timing of the germane message flows associated withpreestablished VPCs between each Packet Handler and each associatedradio port, where only the VCIs at the end points (e.g., the radio portand Packet Handler) need to be selected when a handoff₋₋ requestarrives.

In this scenario, virtual paths (in both directions) between radio portsand the Packet Handler are pre-established. These paths are preferablyidentified by the VPI field in the ATM cell header. The VCI field in theATM cell header is then used to identify the particular call or thecorresponding hand-off route for a given call. In this case, an OA&Mcell on the pre-established VPC between the radio port and the PacketHandler is used to transport an establish₋₋ VC request message to thePacket Handler. The Packet Handler Channel Management Subsystem in turnpicks a VC identifier and sends a confirm₋₋ VC message to the radioport. With the activation of this VCI, a connection is establishedbetween the radio port and the Packet Handler. Once the duplex VCCbetween the radio port and Packet Handler is established, the remainderof the hand-off procedure is completed as described in Section 5.2.1.

4.4.2.3 Slow Hand-off: No Pre-established Virtual Connections

When either (1) VC/VCs are not pre-established (i.e., fast hand-off isnot supported by the embodiment) or (2) the Target Radio Port is notassociated with the Packet Handler of the call, then a slow hand-off,which requires complete connection establishment at the time ofhandoff₋₋ request, can be accomplished through either (1) permanentvirtual paths (VPs) established between Packet Handlers, or (2) or acomplete VP/VC establishment can be completed at the hand-off request.The timing of the germane message flows associated with the latter isshown in FIG. 19.

As shown in FIG. 19, the handoff₋₋ request is directly forwarded by theradio port via the Control Channel Message Handling Subsystem to theWireless-Wired Gateway Control Manager. The Wireless-Wired GatewayControl Manager, using standard procedures, contacts the Channel Managerof the Packet Handler carrying the call and the Radio Port ChannelManager to establish a VCC for the call. Once the VCC is established theWireless-Wired Gateway Control Manager informs the Radio Port ChannelManager to continue with the rest of the hand-off scenario, as in thecase of the fast hand-off.

It is understood that the above described embodiments are merelyillustrative of the application of principles of the invention and thatother arrangements may be devised without departing from the spirit andscope of the invention.

What is claimed is:
 1. A method for establishing a downlink virtualcircuit comprising:receiving, at a radio port, a virtual circuitidentifier from a wireless terminal; attaching said virtual circuitidentifier to an OA&M cell; sending a set-reverse-VC message in saidOA&M cell; transmitting, from said radio port, said OA&M cell to a radioport manager over an uplink virtual circuit; receiving said OA&M cell bya switch in said uplink virtual circuit; reading said set-reverse-VCmessage; and in response to said set-reverse-VC message, establishingsaid downlink virtual circuit in said switch.
 2. The method of claim 1further comprising transmitting from said radio port manager to saidradio port a handoff confirmation message.
 3. A method for establishinga downlink virtual circuit comprising:creating a plurality of virtualcircuit identifiers, each of which is associated with the others;transmitting said plurality of virtual circuit identifiers to a wirelessterminal via a first radio port; communicating with said wirelessterminal via said first radio port with one of said plurality of virtualcircuit identifiers; receiving, at a second radio port, another one ofsaid plurality of virtual circuit identifiers from said wirelessterminal; attaching said another one of said plurality of virtualcircuit identifiers to an OA&M cell; sending a set-reverse-VC message insaid OA&M cell; transmitting, from said second radio port, said OA&Mcell to a radio port manager over a uplink virtual circuit; receivingsaid OA&M cell by a switch in said uplink virtual circuit; reading saidset-reverse-VC message by said switch; and in response to saidset-reverse-VC message, establishing said downlink virtual circuit insaid switch.
 4. The method of claim 3 further comprising communicatingconcurrently with said wireless terminal via said first radio port withsaid one of said plurality of virtual circuit identifiers and via saidsecond radio port with said another one of said plurality of virtualcircuit identifiers.